The present invention relates to an enzyme that can be used for the formation of acetoin, in particular (+)-acetoin.
Acetoin is a constituent of the flavoring component which is produced, for example, by Streptococcus lactis ssp. diacetvlactis. Besides acetoin, this bacterium produces diacetyl, 2,3-butylene glycol and C.sub.2 compounds such as ethanol, acetic acid and acetaldehyde (see, for example, P. Schmitt et al., Appl. Microbiol. Biotechnol. 29: 430-36 (1988)). The bacterium is often added to dairy products like butter because of this flavor production. It is not customary to fractionate these components, for example, to isolate acetoin. Optically-active acetoins and, for example, 2-hydroxy-4-pentanone, are also of interest as chiral synthons for stereospecific syntheses.
Chemically-prepared acetoin is a racemic mixture of (+) and (-) components and is not suitable in this form as, for example, a foodstuff additive. Resolution of the chemically-prepared mixture is, as it is with most racemates, elaborate and cost-intensive.
Usually employed for this purpose are enzymes which convert one isomer, followed by separation of the compounds. A process of this type has not been disclosed for acetoin, and optically-active acetoin is not commercially available anywhere.